This invention relates to a rotor for a superconducting rotating electric machine, and in particular to a rotor in which the coils of the rotor winding are reliably restrained against circumferential forces.
In a superconducting rotating electric machine, the rotor winding is subjected to very great forces in the circumferential direction during operation. It is essential that the coils of the winding be restrained from moving under these forces, since the heat of friction generated by any movement may be sufficient to cause a loss of superconductivity.
The conventional method of restraining the coils of a rotor winding against movement is to insert some sort of rigid retaining member, which extends over all or a considerable portion of the depth of each coil, between the sides of the coil and the sides of the coil slot in which the coil is housed. For example, Japanese Laid Open Patent Application No. 57-166838 discloses a rotor for a superconducting rotating electric machine in which the coils of the rotor are restrained by a pair of retaining members such as wedges which are both inserted between one side of a coil and one side of the slot in which the coil is housed, the restraining members extending for the entire depth of the coil. One of the retaining members serves to protect the sides of the coil while the other retaining member is being pounded into the slot. These retaining members can effectively restrain the entire coil, but they are not entirely satisfactory. Namely, if a coil is not uniformly wound with respect to all of its layers, one or more layers of the coil may be able to move inside the slot, even though the coil as a whole is securely restrained. If this layer or layers moves during operation of the rotor, a loss of superconductivity may ensue due to the frictional heat generated by the movement.